/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cache.annotation;

import java.util.ArrayList;
import java.util.List;

import org.springframework.context.annotation.AdviceMode;
import org.springframework.context.annotation.AdviceModeImportSelector;
import org.springframework.context.annotation.AutoProxyRegistrar;
import org.springframework.util.ClassUtils;

/**
 * Selects which implementation of {@link AbstractCachingConfiguration} should be used
 * based on the value of {@link EnableCaching#mode} on the importing {@code @Configuration}
 * class.
 *
 * <p>Detects the presence of JSR-107 and enables JCache support accordingly.
 *
 * @author Chris Beams
 * @author Stephane Nicoll
 * @since 3.1
 * @see EnableCaching
 * @see ProxyCachingConfiguration
 */
public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {

	private static final String PROXY_JCACHE_CONFIGURATION_CLASS =
			"org.springframework.cache.jcache.config.ProxyJCacheConfiguration";

	private static final String CACHE_ASPECT_CONFIGURATION_CLASS_NAME =
			"org.springframework.cache.aspectj.AspectJCachingConfiguration";

	private static final String JCACHE_ASPECT_CONFIGURATION_CLASS_NAME =
			"org.springframework.cache.aspectj.AspectJJCacheConfiguration";


	private static final boolean jsr107Present = ClassUtils.isPresent(
			"javax.cache.Cache", CachingConfigurationSelector.class.getClassLoader());

	private static final boolean jcacheImplPresent = ClassUtils.isPresent(
			PROXY_JCACHE_CONFIGURATION_CLASS, CachingConfigurationSelector.class.getClassLoader());


	/**
	 * {@inheritDoc}
	 * @return {@link ProxyCachingConfiguration} or {@code AspectJCacheConfiguration} for
	 * {@code PROXY} and {@code ASPECTJ} values of {@link EnableCaching#mode()}, respectively
	 */
	@Override
	public String[] selectImports(AdviceMode adviceMode) {
		switch (adviceMode) {
			case PROXY:
				return getProxyImports();
			case ASPECTJ:
				return getAspectJImports();
			default:
				return null;
		}
	}

	/**
	 * Return the imports to use if the {@link AdviceMode} is set to {@link AdviceMode#PROXY}.
	 * <p>Take care of adding the necessary JSR-107 import if it is available.
	 */
	private String[] getProxyImports() {
		List<String> result = new ArrayList<>();
		result.add(AutoProxyRegistrar.class.getName());
		result.add(ProxyCachingConfiguration.class.getName());
		if (jsr107Present && jcacheImplPresent) {
			result.add(PROXY_JCACHE_CONFIGURATION_CLASS);
		}
		return result.toArray(new String[result.size()]);
	}

	/**
	 * Return the imports to use if the {@link AdviceMode} is set to {@link AdviceMode#ASPECTJ}.
	 * <p>Take care of adding the necessary JSR-107 import if it is available.
	 */
	private String[] getAspectJImports() {
		List<String> result = new ArrayList<>();
		result.add(CACHE_ASPECT_CONFIGURATION_CLASS_NAME);
		if (jsr107Present && jcacheImplPresent) {
			result.add(JCACHE_ASPECT_CONFIGURATION_CLASS_NAME);
		}
		return result.toArray(new String[result.size()]);
	}

}